Tasmanian senator Steve Martin’s decision to join the National Party has drawn a ferocious response from his former party leader Jacqui Lambie, who has labelled him “the country’s loneliest senator”.

In a coup for the Turnbull government, Senator Martin revealed on Monday he would join the Nationals, becoming the party’s only Tasmanian representative at federal or state level.

Senator Martin, who stood as a Jacqui Lambie Network candidate but joined the Senate as an independent after she fell to dual citizenship, has been a reliable vote for the Coalition since joining Parliament.

But his decision to join the Nationals gives the government another guaranteed vote, taking its total number of senators to 31, as it tries to pass legislation through the upper house.

Ms Lambie, who expelled her former candidate from the party after he refused to let her take his place, hit out at Senator Martin on Monday.

Mr Martin says he is the first Nationals senator for Tasmania in almost a century. Photo: AAP

“It looks like a marriage of convenience for two increasingly desperate parties – the drifting Nationals in the post-Barnaby era and the country’s loneliest senator, Steve Martin,” she said.

“It will only get worse as the politics plays out and my fear is that Tasmanians will be used as pawns in the desperate battle for Senate relevance by [Senator] Martin and his new found ‘mates from the bush’.”

While Senator Lambie was a fierce critic of the government, Senator Martin has backed the company tax cuts after extracting various local funding commitments.

“I’m really proud to be the first Nationals senator for Tasmania,” he said on Monday, adding he would be the first Nationals representative in 90 years.

Senator Martin, who will face the voters at the next federal election, garnered only 233 first preferences at the last election, meaning he was unlikely to win re-election as an independent.

The former Devonport mayor said there was “no deal” between him and the party, but argued he was “drawn to the Nationals” due to its focus on regional and rural issues.

Deputy Prime Minister Michael McCormack said getting Senator Martin on board would “reinvigorate” the Nationals in Tasmania.

He likened Senator Martin to a Tasmanian tiger “in the sense that he’s going to be an absolute tiger for regional development”.

Mr McCormack’s Nationals deputy, Bridget McKenzie, said that while watching Senator Martin’s maiden speech, she had thought: “I think deep down you’re one of us.”

Asked about how the Coalition would decide its Senate ticket in Tasmania now the Nationals were active in the state, Senator Martin said it was a matter for the party.

Before he answered the question, Senator McKenzie could be heard suggesting the response to Senator Martin.

For decades the Nationals have been almost invisible in Tasmania, which has been dominated politically by the Liberals, Labor and, to a lesser extent, the Greens.

Senator Martin’s decision to join the Nationals follows Lucy Gichuhi’s move to the Liberals last year, after she refused to join the Australian Conservatives when Family First merged with Cory Bernardi’s breakaway party.

South Australian senator Tim Storer stood as a candidate for the Nick Xenophon Team (now Centre Alliance), but took up his seat as an independent following a dispute with Mr Xenophon.

Fraser Anning, a Queensland senator and former One Nation candidate, refused to stand aside to allow Malcolm Roberts to return to Parliament and is now an independent.

Labor frontbencher Anthony Albanese suggested Senator Martin had failed to respect voters by joining the Nationals.

“Call me old fashioned, I think that voters deserve more respect than members of Parliament just decided to change their political allegiances without reference back to those voters,” Mr Albanese said.